I should preface this post by saying I took a one year break from going to a formal/institutionalized church, and was told many times that I was sinning because I wasn’t attending a Sunday church/worship service.
Scripturally, the only support is by an anonymous author in Hebrews 10:19-25. The verses in question are 24 and 25:
…and let us consider how to stimulate one another to love and good deeds, not forsaking our own assembling together, as is the habit of some, but encouraging one another; and all the more as you see the day drawing nearer.
Now, let me give you the number one rule of interpreting the Bible. The Bible can never mean something today that it did not mean to it’s original audience. You always have to remember that the New Testament was directed to an audience of people that lived between 30-80 A.D., and the Old Testament has an even larger gap for the B.C. crowd.
With that in mind, can Hebrews 10:25’s “assembly” be referring to an institutional church? No. The church system, as we’re familiar with, started with Emperor Constantine around 313AD in accordance to the Edict of Milan, which is a few hundred years after this was written. So, what does assembly mean? Does it mean a formal worship service? The word assembly means just as you would think – people getting together. This could be as small as two people getting together to talk about the Bible, or a thousand people in a building singing songs together.
When the Bible says the assembly is for encouraging, it is to encourage one another. It isn’t for the pastor to preach at you until you are encouraged. No, it is everyone encouraging each other – don’t burden one member of the church with all the encouragement! It is unfair to burden anyone, pastor or not – Jesus said for us to lay our burdens on Him (Matthew 11:28-30).
When I left the church for a year, I still met regularly with Christians, where we sang songs of worship, read our Bibles, prayed for and encouraged each other. In fact, I would say it was more natural for me there than it was at a formal church, so who is neglecting the assembly of the saints?